Meniscal transplant system

ABSTRACT

A workstation having a pair of posts on either side of a clamping plate where a donor bone may be placed on sequentially cut in three separate cutting paths. Cutting gates are attached to the posts and used to provide cutting paths that can be precisely oriented with respect to the meniscus of the donor bone part using visual alignment without any manual measurements. The graft is affixed to a machining clamp and shaved to appropriately shape the sides and form a radius on the bottom of the graft. A tibia is then prepared by using a drill guide to form a pilot hole and then to drill out a large hole for the graft. The drilled hole is expanded and shaped using a rod guide and chisel and then a rasp. The shaped graft may then be implanted into the shaped hole and sutured in place.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/135,772, filed on Mar. 20, 2015.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to meniscal transplant systems, and, moreparticularly, to a meniscal transplant workstation and accompanyingtools for preparing a meniscal transplant and tibial surface andmounting the transplant to a tibia.

2. Description of the Related Art

A damaged human knee joint meniscus may be repaired using a meniscusimplant and integral bone bridge that is shaped to be inserted into acorresponding groove cut in the tibia. As the size, shape and cuts ofdonor implants vary widely, the implant may be positioned in aworkstation so that it can be appropriately shaped using surgical sawsand rasps. Conventional workstations, however, require that the usermanually determine the appropriate measurements and cuts to be performedon the implant and the knee joint to be repaired. As the sitepreparation for the implant is also performed manually, it is oftendifficult to achieve an exact match between the prepared implant and theprepared site. Accordingly, there is a need in the art for a graftworkstation and associated instruments that improve the ease andaccuracy by which such implants and repairs can be made.

BRIEF SUMMARY OF THE INVENTION

The present invention is a system for preparing and implanting ameniscus allograft and integral bone bridge. The invention includes aworkstation having a base and a pair of posts extending upwardly fromthe base to define an axis therebetween. A plate is positioned betweenthe posts to define a horizontal plane. A clamp having an arm extendingover the plate may be used to hold a donor bone in place. A firstcutting gate may be removably coupled to the pair of posts to define afirst cutting path that extends along a first plane that intersects withthe horizontal plane of the plate and that is proximally offset from theaxis of the pair of posts. A second cutting gate may be removablycoupled to the pair of posts to define a second cutting path thatextends along a second plane that is perpendicular to vertical, whereinthe second cutting gate may be adjusted to orient the second plane intoor out of parallel with the horizontal plane. A third cutting gate maybe removably coupled to the pair of posts to define a third cutting paththat extends along a third plane that intersects with the horizontalplane of the plate and that is distally offset from the axis of the pairof posts. In one embodiment, the third cutting gate comprises the firstcutting gate reversibly coupled to the posts. A depth setting groove mayextend along the base of the workstation. The invention also includes aclamp configured to be attached to a graft positioned in the depthsetting groove. The clamp is used to machine the graft using a firstshaver having a first set of blades for shaping the graft into a firstshape. The clamp is also used to machine the graft using a second shaverhaving a second set blades for shaping the graft into a second shapethat is different than the first shape. The workstation may furtherinclude a measuring groove having a profile that corresponds to thefirst and second shapes extending along the base and having indiciapositioned therealong for measuring the length of a graft positioned inthe measuring groove.

For installing the graft in a tibia, the invention comprises a drillguide having a throughbore and an adjustable hook beam that extends froma proximal end through the drill guide proximately to the throughbore toa distal end that may be affixed over a tibia into which a graft is tobe implanted. A pilot guide may be inserted into the throughbore of thedrill guide and a pilot drill bit having a pilot drill stop can beextended through the pilot guide until the pilot drill stop contacts theproximate end of the hook beam. A guide pin can be extended through thethroughbore of the drill guide and a cannulated drill bit having drillstop can be extended through the pilot guide and over the guide pinuntil the drill stop contacts the proximate end of the hook beam to forman implant hole in the tibia into which the graft is to be implanted. Aguide rod may be positioned in the implant hole and a chisel having ahandle that can slidingly advance along the guide rod into the tibia toshape the implant hole until the guide rod extends into the handle ofthe chisel a predetermined distance. A rasp having a cross-sectioncorresponding to the cross-sectional shape of the graft that may beadvanced into the shaped implant hole to shape the hole to exactly matchthe graft prepared using the workstation of the present invention.

The invention comprises a method for preparing a meniscus bone graft. Adonor bone part having a meniscus extending from a pair of meniscalhorns is clamped between a plate extending along a horizontal plane anda clamp of a workstation. A first cutting gate is positioned over a pairof posts extending upwardly from the workstation on either side of theplate to define an axis therebetween. The donor bone part is cut along afirst cutting path defined by the first cutting gate that extends alonga first plane that intersects with the horizontal plane of the plate andthat is proximally offset from the axis of the pair of posts. A secondcutting gate is positioned over the pair of posts and aligning along theaxis that extends between the pair of meniscal horns. The donor bonepart is then cut along a second cutting path defined by the secondcutting gate. A third cutting gate is positioned over the pair of postsand the donor bone part is cut in a third cutting path defined by thethird cutting gate that extends along a third plane which intersectswith the horizontal plane of the plate and that is distally offset fromthe axis of the pair of posts. A graft is thereby formed having threesides defined by the three cutting paths, a native top side having themeniscus naturally attached to the bone implant by its meniscal horns.The graft is then placed into a groove and a clamp is attached to set apredetermined protrusion for the graft. The clamp containing the graftis placed in a slot in the first shaver and moved along a first set ofblades to shape the graft into a first shape. The clamp is also used tomove the graft along a second shaver having a second set of blades toshape the graft into a second shape that is different than the firstshape. The size of the graft can then be checked by placing it in asecond groove of the workstation.

The graft may then be implanted by attaching a trans-tibial drill guidehaving a throughbore and an adjustable hook beam that extends throughthe drill guide from a proximal end to a distal end positioned over atibia into which the graft is to be implanted. A pilot guide is insertedinto the throughbore of the drill guide and a pilot drill bit having apilot drill stop is used to drill a pilot hole into the tibia until thepilot drill stop contacts the proximate end of the hook beam. A guidepin is extended through the throughbore of the drill guide and the pilothole and a cannulated drill bit having drill stop that can be extendedthrough the pilot guide and over the guide pin is used to form animplant hole in the tibia. A guide rod is positioned in the implant holeand a chisel having a handle that can slidingly advance along the guiderod into the tibia is used to shape the implant hole until the guide rodextends into the handle of the chisel a predetermined distance. A rasphaving a cross-section corresponding to the cross-sectional shape of thegraft is then used to shape the implant hole. The graft is then insertedinto the implant hole and the meniscus sutured to the tibia.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

The present invention will be more fully understood and appreciated byreading the following Detailed Description in conjunction with theaccompanying drawings, in which:

FIG. 1 is a perspective view of a workstation according to the presentinvention;

FIG. 2 is a perspective view of a donor bone graft to be prepared on aworkstation according to the present invention; and

FIG. 3 is a perspective view of a donor bone graft positioned on aworkstation according to the present invention;

FIG. 4a is a perspective view of a first cutting fence on a workstationaccording to the present invention;

FIG. 4b is a sectional view of the first cutting fence on theworkstation taken along x---x of FIG. 4a according to the presentinvention;

FIG. 5 is a perspective view of a second cutting fence on a workstationaccording to the present invention;

FIG. 6 is another perspective view of a second cutting fence on aworkstation according to the present invention;

FIG. 7a is a perspective view of a third cutting fence on a workstationaccording to the present invention;

FIG. 7b is a sectional view of the first cutting fence on theworkstation taken along x---x of FIG. 7a according to the presentinvention;

FIG. 8 is a perspective view of a donor bone graft prepared on aworkstation according to the present invention;

FIG. 9 is a perspective view of a workstation and graft clamp accordingto the present invention;

FIG. 10 is another perspective view of a workstation and graft clampaccording to the present invention;

FIG. 11 is a perspective view of a workstation and a first shaveraccording to the present invention;

FIG. 12 is another perspective view of a workstation and a first shaveraccording to the present invention;

FIG. 13 is a perspective view of a workstation and a second shaveraccording to the present invention;

FIG. 14 is a perspective view of another aspect of workstation accordingto the present invention;

FIG. 15 is a perspective view of a tibia and meniscus to be repairedwith a bone graft according to the present invention;

FIG. 16 is another perspective view of a tibia and meniscus to berepaired with a bond graft according to the present invention

FIG. 17 is a perspective view of drill guide according to the presentinvention;

FIG. 18 is a perspective view of drill guide and tibia according to thepresent invention;

FIG. 19 is a perspective view of drill guide with a pilot drill guideaccording to the present invention;

FIG. 20 is a perspective view of drill guide with a pilot drill guideand pilot drill bit according to the present invention;

FIG. 21 is a perspective view of drill guide with a drill guide pinaccording to the present invention;

FIG. 22 is a perspective view of drill guide with a guide pin insertedinto a tibia according to the present invention;

FIG. 23 is a perspective view of drill guide with pilot drill guidepartially removed according to the present invention;

FIG. 24 is a perspective view of a cannulated drill bit being insertedover a guide pin into a tibia according to the present invention;

FIG. 25 is a perspective view of a cannulated drill bit fully insertedover a guide pin into a tibia according to the present invention;

FIG. 26 is a perspective view of a guide rod according to the presentinvention;

FIG. 27 is a perspective view of a chisel and a guide rod inserted intoa tibia according to the present invention;

FIG. 28 is a perspective view of a chisel fully inserted into a tibiaaccording to the present invention;

FIG. 29 is a perspective view of the handle of a chisel according to thepresent invention;

FIG. 30 is a perspective view of a rasp according to the presentinvention;

FIG. 31 is a perspective view of a rasp inserted in to a tibia accordingto the present invention;

FIG. 32 is a perspective view of a meniscus graft prepared according tothe present invention for implantation into a tibia prepared accordingto the present invention; and

FIG. 33 is a perspective view of a meniscus graft prepared according tothe present invention implanted into and sutured to a tibia according tothe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, wherein like numerals refer to like partsthroughout, there is seen in FIGS. 1 and 2 a workstation 10 forpreparing an allograft donor bone graft 12 for implantation into thetibia of a patient. Graft 12 typically comprises a hemi-tibial plateaubone portion 14 having a saw cut surface 16 and an attached meniscus 18extending from the top side 20 of bone portion 14 via two meniscalattachment horns 22 and 24.

Workstation 10 comprises a base 30 supporting a clamp 32 aligned over acentral plate 34 having surface 36 with features, such as checkering ortexturing that is machined therein, so that graft 12 can be securelyclamped in place on workstation 10. Clamp 32 comprises a threaded post38 extending upwardly from base 30, a clamping arm 40 coupled to postand extending over plate 34, and a threaded wheel 42 that can beadvanced up or down post 38 via rotational movement to bring clampingarm 40 into secure engagement with graft 12 when it is positioned onplate 34. Post 38 may be keyed to arm 40 so that arm 40 does not rotatearound post 38. Referring to FIG. 3, base 30 further includes visualalignment indicia 44 and 46 for use in aligning the two meniscal horns22 and 24 (shown as disposed along axis A-A on graft 12) therewith whengraft 12 is placed onto plate 34 and clamped in place by clamp 32. Base30 additionally supports a pair of guide posts 48 and 50 that arepositioned on opposing sides of and proximately of plate 36. When graft12 is properly positioned on plate 34 and clamped in place by clamp 32,saw cut 16 of graft 12 will extend over the proximate edge of plate 36between guide posts 48 and 50. In this manner, workstation 10 allowsgraft 12 to be easily aligned for subsequent cutting operations to forman implant with precise dimensions for insertion into a similarlydimensioned receiving trough formed into the tibia of a patient.

Referring to FIG. 4a , a first cutting gate 52 having a slot 54 formedtherein for accepting an oscillating planar saw blade 78 may bepositioned over graft 12 by mounting it on posts 48 and 50 of base 30.FIG. 4b shows a sectional view of the first cutting gate 52 along x----xin FIG. 4a . First cutting gate 52 includes a pair of bosses 56 and 58positioned at either end thereof that are adapted to accept guide posts48 and 50, respectively, so that cutting gate 52 is securely held abovegraft 12. Bosses 56 and 58 may be keyed to posts guide posts 48 and 50to prevent improper installation of first cutting gate 52. First cuttinggate 52 is used to guide saw blade 78 to form a first cutting path alongthe front of graft 12 that is parallel to the axis A-A of meniscal horns22 and 24. Saw cut 16, which can be very irregular and imprecise when itis formed to remove graft 12 from the tibia of a donor, is removed andreplaced with a new cut that is precisely oriented relative to meniscalhorns 22 and 24. Slot 54 of first cutting gate 52 is also oriented sothat the first cutting path is angled slightly away from vertical so thenewly formed cut in graft 12 has a slight bevel and is wider toward thebottom side of graft 12 relative to meniscal horns 22 and 24 on the topside 20 of graft 12. Preferably, first cutting gate 52 provides a firstcutting path that is offset from vertical by about five degrees. Slot 54of first cutting gate 52 is also offset from the axis of posts 48 and 50so that the resulting cut is proximate to the axis of posts 48 and 50 apredetermined distance, as well as parallel thereto. As a result, thecut along first cutting path will be a predetermined distance in frontof meniscal horns 22 and 24, which are intended to be aligned so thattheir axis A-A is aligned along the axis of posts 48 and 50 and theindicia provided therewith. The amount of offset is preferably one-halfof the desired width of the final prepared graft 12 because, asexplained below, first cutting gate 52 may also be used to form theopposite face of graft 12. In the example illustrated in the presentapplication, the offset is five millimeters to produce a final graft 12having a width of ten millimeters.

Referring to FIG. 5, a second cutting gate 60 having a slot 62 formedtherein for accepting a saw blade 78 may be positioned over graft 12using a pair of bosses 66 and 68 at either end that are adapted toaccept guide posts 48 and 50, respectively. Slot 62 of second cuttinggate 60 is formed in a movable fence 70 interconnected to bosses 66 and68 by a pair of knobs 72 and 74 that may be rotated to loosen andtighten the connection between fence 70 and bosses 66 and 68 so thatfence 70 can be pivoted relative to bosses 66 and 68 so that the upperedge 76 of fence 70 can be aligned with meniscal horns 22 and 24. Fence70 may thus be oriented along an axis that is non-perpendicular the axisof posts 48 and 50 using the upper edge 76 of fence 70 as a visual guideto define a cutting path that extends along a plane that is parallel tothe axis formed by meniscal horns 22 and 24, which may not be parallelto surface 36 of plate 36. The height of fence 70 may thus bedimensioned so that, once upper edge 76 is aligned with meniscal horns22 and 24, slot 62 will be positioned a predetermined distancedownwardly from meniscal horns 22 and 24. For example, upper edge 76 offence 70 can be used to align a cutting path that is precisely 11millimeters below upper surface 20 of graft 12, which avoids the needfor hand measuring and pen marking common in the field for thisparticular cut. Slot 62 of second cutting gate 60 thus produces a secondcut in graft 12 that accurately and precisely defines a predetermineddepth for graft 12 that is also parallel to the axis formed by meniscalhorns 22 and 24 due to the alignment of fence 70 with meniscal horns 22and 24. As seen in FIG. 6, workstation 10 may be reoriented so that sawblade 78 can be inserted downwardly into slot of second cutting gate 60and used to cut graft 12. Saw blade 78 can be inserted past the distancenecessary to define the depth of graft 12 as a subsequent cut willdetach the desired graft 12 and associated meniscus 18 from thesurrounding bone of original graft 12.

Referring to FIG. 7a , a third cutting gate 80 having a slot 82 formedtherein for accepting a saw blade 78 may be positioned over graft 12using a pair of bosses 86 and 88 at either end that are adapted toaccept guide posts 48 and 50, respectively. FIG. 7b shows a sectionalview of the third cutting gate 80 along x----x in FIG. 7a . Thirdcutting gate 80 is oriented to define a third cutting path that isangled slightly distally away from vertical so the newly formed rearface of graft 12 has a slight bevel and is wider toward the bottom sideof graft 12 relative to meniscal horns 22 and 24. Third cutting gate 80is also offset distally from posts 48 and 50 (and axis A-A of meniscalhorns 22 and 24) so that the third cutting path is positioned to therear side of posts 48 and 50 and on the other side of meniscal horns 22and 24 from the first cutting path established by the first cutting pathof first cutting gate 52. Saw blade 78 may then be applied through slot82 to cut graft 12 along the third cutting path. Third cutting gate 80may comprise first cutting gate 52 positioned on workstation 10 in areversed orientation so that the offset of first cutting gate 52 istoward the back of workstation 10 and on the opposite side of meniscalhorn 18. In this approach, the front and rear sides of first cuttinggate 52 should be clearly marked so that first cutting gate 52 isappropriately positioned by a user when used as either first cuttinggate 52 or third cutting gate 80. In addition, keying of posts 48 and 50relative to bosses 86 and 88 (which may also be bosses of 56 and 58 offirst cutting gate 52), can allow for reversal but not upside downattachment to posts 48 and 50. The width of the cut graft 12 will thusbe twice the amount of offset of slot 52 relative to the axis of posts48 and 50. In other words, an offset of 5 millimeters will produce graft12 having an approximate width of 10 millimeters (not accounting for theslight taper of first cutting path). More specifically, as seen in FIG.8, sawing donor graft 12 along first cutting path X-X, second cuttingpath Y-Y and third cutting path Z-Z results in a final graft 12 havingan isosceles trapezoidal cross-section with meniscus 18 extending fromthe top side 22 of graft 12, which is narrower than the base of theisosceles trapezoid cross-sectional shape. First cutting path X-X andthird cutting path Z-Z are both offset from vertical by about 5 degreesso that graft 12 tapers inwardly toward second cutting path Y-Y.

Referring to FIG. 9, base 30 further comprises a depth setting groove 92that is dimensioned to accept trapezoidal graft 12 therein. Oncetrapezoidal graft 12 is positioned in groove 92, a graft clamp 94 may befitted over graft 12. Graft clamp 94 comprises a fixed member 96 and anopposing moveable member 98 that can moved into and out of secureengagement with graft 12. As seen in FIG. 10, graft clamp 94 ispositioned around graft 12 and seated onto workstation 10. Using anadjustment knob 100 having a threaded shaft 102 interconnected tomoveable member. Groove 92 has a predetermined depth corresponding tothe desired depth of graft 12 so that subsequent milling using graftclamp 94 as a milling guide will not remove more material from graft 12than is needed to prepare graft 12 for implantation but will allow theappropriate radius to be formed in the bottom of graft 12. For example,5 millimeter should extend below graft clamp 94 so that subsequentmachining provides the appropriately shaped graft 12. Fixed member 96may include a protrusion 104 that seats in an alignment groove 106 thatextends along workstation 10 parallel to depth setting groove 92. Ifgraft 12 is fully seated in groove 92 and graft clamp 94 affixed theretoso that graft clamp 94 is resting on workstation 10, graft clamp 94 canbe used as a machining guide to ensure that graft 12 is preciselymachined into the desired dimensions prior to implantation. Bothcontacting portions of graft clamp 94 may have checkered, textured orspiked surfaces for using suitable approaches, such as, milling with aCNC machine. The exact pattern of the checkering or texturing isunimportant as long as the pattern sufficiently fixes the position ofthe nearly completed donor part in the graft clamp 94 so that it doesnot move with respect graft clamp 94 during subsequent operations thatcreate the final rounded edge of graft 12 prior to implantation.

Referring to FIG. 11, a first shaver 110 may be secured to workstation10 by positioning a pair of opposing holes 112 and 114 formed in firstshaver 110 over guide posts 48 and 50. Graft clamp 94 may then be placedagainst first shaver 110 so that the bottom of graft 12 is in engagementwith a shaving channel 116 of first shaver 110. An alignment channel 118that accepts protrusion 104 extends parallel to shaving channel toensure graft 12 is moved precisely longitudinally along shaving channel116. Graft clamp 94 may then be moved along the surface of first shaver110 so that shaving channel 116 removes material from graft 12, as seenin FIG. 12. As explained above, graft clamp 94 thus acts as a machiningguide and ensures that the appropriate amount of material is removedfrom graft 12 to precisely form the desired dimensions of graft 12.First shaver 110 is preferably used to preshape the underside of graft12 to facilitate subsequent operations. Once shaving is completed, asecond shaver 120 may be secured to workstation 10 by positioning a pairof opposing holes 122 and 124 formed in second shaver 120 over guideposts 48 and 50, as seen in FIG. 13. Graft clamp 94 may then be used toposition the bottom of graft 12 in a second shaving channel 126 withprotrusion 104 in an alignment channel 128. Clamp 94 may then be used tomove graft 12 along second shaver 120 so that second shaving channel 126removes the appropriate material from the bottom of graft 12 to form thedesired radius of curvature for the bottom of graft 12. Once secondshaver 120 has been used, graft 12 is removed from graft clamp 94.

Referring to FIG. 14, workstation 10 includes a trial slot 130 isdimensioned to accept graft 12 after it has been shaved by first shaver110 and second shaver 120. More particularly, trial slot 130 has abottom 132 with a radius corresponding to the newly formed radius ofgraft 12. Trial slot 130 is associated with indicia 134 on workstation12 that is indexed to allow for an easy visual determination of thelength of graft 12. The length of graft 12 may be trimmed using trialslot 120 to the appropriate length for implantation so that the meniscalhorns 22 and 24 are located in the appropriate position when graft 12 isimplanted into a tibia prepared according to the present invention, asexplained below.

Workstation 10 and its associated components discussed above may be madefrom any suitable material, such as stainless steel (e.g., 17-4PHstainless steel or NITRONIC 60). Any numbers or lettering can be madeusing a suitable marking method, such as laser etching. Components mayalso be passivated after laser etching according to ASTM A967 orASM-QQ-P-35.

Referring to FIG. 15, the tibia 140 of a patient may be prepared byperforming a menisectomy and removing any debris associated with themeniscus to be replaced, such as by using a shaver 142. As seen in FIG.16, a notch 144 is formed in the tibial eminence.

Referring to FIG. 17, the invention further comprises a drill guide 150having a handle 152 extending from a main body 154 having a throughbore156 and a spacer 158 for engaging and spacing main body 154 apredetermined distance from a tibia 140. An adjustment wheel 160 ispositioned around throughbore 156 and interconnected to a hook beam 162that extends through main body 160 above throughbore 156. Hook beam 162extends outwardly from drill guide 150 to define an adjustable tibiareceiving space 164 between a curved end 166 of hook beam 162 and spacer158. Hook beam 162 has multi-start threads 166 formed therein thatinterconnect to threads on the inside of adjustment wheel 160 so thathook beam 162 can be extended over tibia 140 and then retracted tosecure tibia 140 in tibia receiving space 164 between curved end 166 ofhook beam 162 and spacer 158 of main body 154 by turning adjustmentwheel 160, as seen in FIG. 18. Preferably, adjustment wheel 160 hasmulti-start threads so that hook beam 162 is advanced quickly whilereducing the risk of overtightening due to the reduced torque that ispossible. Hook beam 162 is calibrated so that the distance from itsproximal end to curved end 166 is known and thus, when connected to atibia, provides a gauge so that the depth of subsequent drillingoperation can be coordinated to prevent overdrilling, such as byallowing for a safe stopping distance of about 5 millimeters.

Referring to FIG. 19, a pilot guide 170 having a narrow through bore 172that is dimensioned to receive a pilot drill bit 174 may be insertedinto throughbore 156 of drill guide 150 and locked into position viarotation of pilot guide 170 so that a cam on pilot guide 170 interlockswith the underside of hook beam 162. Pilot guide 170 should preferablycontact tibia 140 securely to prevent drill bit slippage across thesurface of tibia 140.

Referring to FIG. 20, a pilot drill bit 174 may then be passed throughthe narrow throughbore 172 of pilot guide 170 and used to drill a pilothole in tibia 140. Pilot drill bit 174 is associated with a drill stop176 that will engage the proximal end of hook beam 162 when bit 174traverses a predetermined distance into tibia 140 and thus prevent overinsertion of pilot drill bit 174 into tibia 140. Preferably, drill stop176 allows for at least about 5 millimeters of spacing between the endof pilot drill bit 174 and curved end 166 of hook beam 162 to ensurethat drilling does not extend through the distal side of tibia wheredamage can occur to any of the major blood vessels in that area. Itshould be recognized the appropriate positioning of drill stop 176 willdepend on various factors, such as the length of hook beam 162, and canbe calculated and established in advance based on the particularcircumstances. In other words, the lengths of hook beam 162 and drillbit 174 are interrelated and correlated to each other to ensure againstoverdrilling without the need for a surgeon to take depth measurementsduring drilling operations.

Referring to FIGS. 21 and 22, once a pilot hole has been formed in tibia140, a blunt guide pin 180 having indexing marks 182 and 184 may beinserted into the pilot hole by inserting guide pin 180 through narrowthroughbore 172 of pilot guide 170. Indexing of guide pin 180 may beused to confirm that the pilot hole has been drilled to an appropriatedepth as one indexing mark 182 or 184 should align with the proximateend of hook beam when properly inserted to the appropriate depth intothe pilot hole. Guide pin 180 is blunted to ensure that any frictionalengagement during subsequent drilling does not advance guide pin 180further into tibia 140. Pilot guide 170 may then be unlocked from drillguide 150 and removed, as seen in FIG. 23, leaving guide pin 180 inplace.

Referring to FIG. 24, a cannulated drill bit 190 having a throughbore192 for receiving guide pin 180 may be inserted into throughbore 156 ofdrill guide 150 while guide pin 180 is received in throughbore 192 ofdrill bit 190. Drill bit 190 may then be used to drill a larger hole intibia 140, as seen in FIG. 25. Drill bit 190 preferably includes a drillstop 194 that is positioned to engage the proximate end of hook beam 162of drill guide 150 when drill bit 190 has been inserted an appropriatedepth to, once again, prevent over-insertion of drill bit 190. It shouldbe recognized the appropriate positioning of drill stop 194 will dependon various pre-established factors, such as the length of hook beam 162and desired depth of the hole in tibia, and can be calculated andestablished in advance based on the particular circumstances. Once thehole 196 is drilled, drill guide 150 and all components are removed fromsite.

Referring to FIG. 26, a guide rod 200 comprising a shaft 202 having afirst set of indexing at one end 204 at a second set of indexing at theopposing end 206 may be inserted into hole 196 in tibia 140. As seen inFIG. 27, guide rod 200 acts as a guide for a chisel 208 having a lowerchannel 210 dimensioned to slide along the upper surface 212 of guiderod 200 and a pair of opposing blades 214 and 216 positioned above thelower channel 210 to remove bone from tibia 140 along the sides of hole196 to match the profile of graft 12. Guide rod 200 may incorporate aflat along its upper surface upon which a corresponding horizontal bladeelement of chisel 208 may be located in order to prevent the entrapmentof bone fragments that could potentially cause chisel 208 and guide rod200 to jam. Guide rod 200 may include indicia thereon to ensure that itis properly oriented when inserted into tibia 140, e.g., a legend suchas “THIS SIDE UP” may be used. Indexing on ends of guide rod 200indicate the distance from the respective ends of guide rod 20, and thusindicate the depth of hole 196 and the distance that chisel 208 hastravelled along guide rod 200 into hole 196. Referring to FIG. 28,chisel 208 has a handle 218 with a window 220 formed therein so thatindexing of guide rod 200 is clearly visible therethrough. Chisel 208may be slidingly engaged over guide rod 200 and driven into tibia 140 toenlarge and shape hole 196 in tibia 140. As seen in FIG. 29, chisel 208contains a stop 222 and associated indicia (such as a “STOP” line) onhandle 218 that indicates, via movement of guide rod 200 inside window220, how far to drive chisel 208 into hole 196. As explained above withrespect to hook beam 162, a safe depth of hole 196 can be ensured bystopping the progress of bone removal when an inserted tool reaches anappropriate depth by using a gauge that is positioned in the hole 196and used to stop the progress of the tool, such as stop 222 on theinside of chisel 208 that is reached when chisel 208 advances over guiderod 200, which acts the appropriate depth gauge. Once chiseling iscomplete, chisel 208 and guide rod 200 may be removed from hole 196.

Referring to FIG. 30, a rasp 230 having a U-shaped cross-section 232corresponding to the profile of graft 12 may be inserted into hole 198of tibia 140 if hole 198 does not have exactly the same profile as graft12. Rasp 230 is used to remove material from hole 198 so that rasp 230has the predetermined shape and dimensions of graft 12 when preparedusing workstation 10 as explained above, as seen in FIG. 31. It shouldbe recognized that the shape and dimensions of rasp 230 are selected tocorrespond to the shape and dimensions of graft 12 once appropriatelycut and shaved using workstation 10, and vice versa.

Referring to FIG. 32, graft 12 may be positioned in tibia 140 by placingremaining bone portion 14 of graft 12 in the shaped hole 198 in tibia140 so that meniscus 18 is appropriately positioned over the top oftibia 140 where the damaged meniscus was located prior to removal. Dueto precise alignment and cutting of graft 12 on workstation 10, graft 12will match the profile of hole 198 exactly and meniscal horns 22 and 24will in the appropriate position so that meniscus 18 is in the properlocation on the top of tibia 140 Once graft 12 and meniscus 18 areproperly positioned, the graft meniscus 18 attached to the remnant ofthe patient's original meniscus by inserting a series of sutures 236around the upper edge of tibia 140 as seen in FIG. 33.

The various tools for preparing tibia 140 as discussed above may be madefrom any suitable material, such as stainless steel (e.g., 17-4PHstainless steel or NITRONIC 60). Any numbers or lettering can be madeusing a suitable marking method, such as laser etching. Components mayalso be passivated after laser etching according to ASTM A967 orASM-QQ-P-35.

What is claimed is:
 1. A system for preparing a meniscus bone grafthaving a bone portion and a meniscus extending from the bone portion bya pair of meniscal horns, comprising: a workstation having a baseextending along a horizontal plane between a first end and a second endopposite to the first end, opposing first and second sides, and havingtop and bottom surfaces; a pair of posts extending upwardly, alongparallel longitudinal axes, from and fixed to the top surface of thebase adjacent the opposing first and second sides at the first end ofthe base, the pair of posts intersecting the horizontal plane atperpendicular angles and defining a traversing axis extendingtherebetween; a plate positioned between the posts on the top surface ofsaid base and defining the horizontal plane; a clamp having a postextending upwardly from the top surface of the base at the second end ofthe base, and an arm coupled to said post and extending over the plateconfigured to affix the bone graft on the plate; a first cutting gatehaving a superior end and an inferior end, and a first pair of bosses,each of said first pair of bosses includes a through opening extendingfrom said superior end to said inferior end, wherein said inferior endis closer than said superior end to the top surface of the base of theworkstation when said pair of posts are slidably received through thethrough openings of said first pair of bosses, the first cutting gate isconfigured for being removably coupled to the pair of posts, the firstcutting gate includes a first cutting slot extending therethroughbetween said first pair of bosses, and defining a first cutting pathextending from said superior end of the first cutting gate to saidinferior end of the first cutting gate along a first plane thatintersects with the horizontal plane of the plate at an oblique angle,and being offset from the traversing axis of the pair of posts towardthe first end of the base of the workstation when the pair of posts areslidably received through the first pair of bosses of the first cuttinggate; a second cutting gate independent from the first cutting gateconfigured for being removably coupled to and moveable along the pair ofposts by inserting the pair of posts through openings in the secondcutting guide, said second cutting gate having a cutting slot to defineand select a second cutting path from a plurality of potential secondcutting paths that extends along a second plane that is parallel to thehorizontal plane when said second cutting gate is coupled to the pair ofposts and is configured to be adjusted relative to the plate to bealigned with an axis extending between the pair of meniscal horns of themeniscus bone graft when the meniscus bone graft is positioned on theplate; a third cutting gate independent from the first cutting gate andindependent from the second cutting gate having a superior end and aninferior end, wherein the inferior end is closer than the superior endto the base of the workstation when the third cutting gate is coupled tothe pair of posts, the third cutting gate is configured for beingremovably coupled to the pair of posts by sliding the pair posts throughopenings in the third cutting gate, said third cutting gate includes athird cutting slot defining a third cutting path extending from thesuperior end of the third cutting gate to the inferior end of the thirdcutting gate along a third plane that intersects with the horizontalplane at an oblique angle, and being offset from the traversing axis ofthe pair of posts toward the second end of the base of the workstationwhen the third cutting gate is coupled to the pair of posts.
 2. Thesystem of claim 1, wherein the third cutting gate is capable of beingreversibly coupled to the pair of posts.
 3. The system of claim 2,further comprising a depth setting groove extending along the base. 4.The system of claim 3, further comprising a clamp configured to beattached to a graft positioned in the depth setting groove.
 5. Thesystem of claim 4, further comprising a first shaver having blades forshaping the graft into a first shape.
 6. The system of claim 5, furthercomprising a second shaver having blades for shaping the graft into asecond shape that is different than the first shape.
 7. The system ofclaim 6, further comprising a measuring groove having a profile thatcorresponds to the first and second shapes extending along the base andhaving indicia positioned therealong for verifying the length and thecross-sectional shape of a graft positioned in the measuring groove. 8.The system of claim 7, further comprising a drill guide having athroughbore and an adjustable hook beam that extends from a proximal endthrough the drill guide throughbore to a distal end that may be affixedover a tibia into which a graft is to be implanted.
 9. The system ofclaim 8, further comprising a pilot guide that can be inserted into thethroughbore of the drill guide and a pilot drill bit having a pilotdrill stop that can be extended through the pilot guide until the pilotdrill stop contacts the proximate end of the hook beam.
 10. The systemof claim 9, further comprising a guide pin that can be extended throughthe throughbore of the drill guide and a cannulated drill bit havingdrill stop that can be extended through the pilot guide and over theguide pin until the drill stop contacts the proximate end of the hookbeam to form an implant hole in the tibia into which the graft is to beimplanted.
 11. The system of claim 10, further comprising a guide rodthat may be positioned in the implant hole and a chisel having a handlethat can slidingly advance along the guide rod into the tibia to shapethe implant hole until the guide rod extends into the handle of thechisel a predetermined distance.